This research proposes to isolate and characterize neoantigens, present on mammary carcinoma cells, which are detected by human monoclonal antibodies (Mabs). We will study any homology between the neoantigens and the known growth factors and their receptors whose expression has been reported to be associated with malignancies. The investigation will help us understand how neoantigens play roles in malignant transformation and may lead to the discovery of new growth factors and their receptors. Antibodies present in the serum of patients with mammary carcinomas have been shown to be reactive with malignant cells, suggesting the expression of "neo-antigens" on those cells. Furthermore, the existence of such antigens recognized by host immune system indicate the presence of sensitized B lymphocytes in those patients. In order to perform these experiments, the "neo-antigens" from tissues of breast carcinomas or cell line will be identified, isolated, and characterized using human Mabs. The commercially available antibodies to known growth factors and their receptors will serve to identify their homology with the purified antigens. The purified antigens will also be tested for the effect on growth in vitro of human mammary epithelial cells. Normal breast tissue will serve as normal controls. Preliminary studies have established the feasibility of several stages of this proposal up to and including the generation of cloned hybrids which are stable for the secretion of human Ig for over two years, plus the development of immunoperoxidase procedure of utilizing these antibodies for the detection of antigens in tissues. The human Mabs have shown preferential binding to malignant as compared to normal mammary epithelial cells. Also, tee preliminary studies have shown the feasibility of isolating the antigens by using immobilized human Mabs. The approach outlined here will facilitate the: (1) generation of human monoclonal antibodies to breast neoantigens; (2) isolation and characterization of the antigens; (3) determination whether these antigens are homologous to growth factors and their receptors, some of which have been found to be oncogene products; (4) possible discovery of new growth factors and their receptors; and (5) understanding of the mechanism by which these components may regulate growth and/or differentiation and of stability of phenotypic states. (AG)